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LF Pinhole - design and building

Hoping to get some interest in this aspect of photography, and following the demise of that excellent site f295, I thought Iíd set the ball rolling by describing in more detail how I went about building a camera which I recently mentioned here: http://www.largeformatphotography.in...amera!/page324

A friend on this forum happened to throw in a box of 5x12 x-ray film in a parts swap we did and that got me thinking about a panoramic pinhole camera in this format. The result here followed months of trial and error:

The camera has front rise and fall of +/- 15mm to allow it to be used level and yet ensuring that the horizon remains straight, since the horizon will be curved in a curved film-plane camera if it is tilted up or down. As it turned out I could only find 15mm as Iíd made the frame for the front too wide top and bottom. I havenít yet tested whether this is enough. The camera has a bubble level in the top and sighting dots made from 1Ē painted nails to aid composition.

The first hurdle to overcome was bending the plywood back. This was eventually achieved by scoring the inside surface with vertical Vs spaced at 1cm intervals using a router, then soaking and careful progressive bending over several days, using clamps and weights, then eventually gluing top and bottom to hold it all together. It was a hair-raising experience and I felt several times that I came very close to splitting the wood. In retrospect, Vs at 5mm spacing may have made the bending easier.

I used a 0.5mm EMS (electron microscope) aperture for the pinhole. These are truly excellent - laser drilled precision. Iíve used them before on other cameras with great success. Iíd never think of making my own now. Theyíre available from a guy on f295 at $1 apiece posted. If anyone has contact with Earl, would you mind seeing if heís interested in posting here?

Mounting these pinholes is tricky, since theyíre very small. Some folk use tape with a 1.5mm hole punched in it to grab the pinhole; the pinhole is then taped to the camera front. I donít yet have a punch to allow me to do it this way, but Iíve ordered a couple from China. Meantime I mount my pinholes in a small brass washer, using a couple of blobs of black paint that find their way by capillary action. The pinhole on its washer is then mounted into a recess drilled into the plate (more black paint).

As per my previous post (above) I found vignetting on my first test shot, which I immediately thought was an image circle issue. I thought that I may have to mount the pinhole further forward to fix this. However a member (NedL) was right when he suggested that it was obstruction. Sure enough, although Iíd beveled the exit hole in the rear of the plate, there was still a definite ridge, which Iím sure was responsible. Iíve since ground this down, but have not yet tested it as I have a scratching issue with my developing trays and have to get some glass cut to remedy this. The next pic shows the rear of the plate and also a view of the front showing the clearance needed for rise/fall and horizontal field.

The 0.5mm pinhole is mounted 135mm from the film plane. I had intended it to be 127mm (5Ē), the radius of the film curve, but things donít always turn out as hoped. Fortunately pinhole is very forgiving, and I donít think any unevenness in exposure will show up. At 135mm the speed is f/270. The one test Iíve done suggests that the image is a little soft. Iíll do a few more tests after I sort out my developing issues, and may yet go down to 0.4mm and f/340.

A note on bits and pieces: I now get everything from China via eBay. No doubt about it. Over the years Iíve scoured the country from engineering suppliers to model shops and found sourcing small screws and knobs etc, the type of things so vital to DIY photography, next to impossible. For me eBay is the answer, and knowing how to search is very helpful. Terms like M3 screws for 3mm metric, or knurled knobs, case clips etc usually turn up direct hits or lead to further search clues. The two brass pieces in the last two pics are known in eBay speak as "M3 / M4 Brass Knurled Nuts Insert Embedded Nuts"; I used these as nuts to secure the front panel and as embedded nuts held with epoxy for the front panel to bolt into.

So how about it LF Pinholers? I'm sure there would be much interest in your own pinhole camera building achievements. There is certainly interest in pinhole photography here, as evidenced by the many favourable responses to pinhole images posted here. Love to hear from you.

Re: LF Pinhole - design and building

Barry, that is quite a bit of workmanship. Thanks for the detailed description. I am afraid the extent of my pinhole camera construction is making a lens-board pinhole for my 8X10, 5X7, and 4X5 cameras.

Re: LF Pinhole - design and building

Thanks Dave, and good luck with your adventures into pinhole. Thank you too, Graham. I must say I'm impressed with your website, both pinhole images and your ventures into camera making, both pinhole and the 8x10.

My camera has a way to go yet. Another test shot yesterday still shows vignetting which has resisted my previous attempt to fix it. I think the problem is the thickness of the pinhole mounting plate. I used 2mm aluminium because I didn't have 1mm on hand, and I think the pinhole needs to be further back into the plate. As NedL said previously, vignetting can be hard to fix with a curved film plane.

Re: LF Pinhole - design and building

Yesterday's test. Vignetting cropped out, very minimal work in LR. A bit too close to the subject; I'll have to get used to vertical composition - horizontal is no problem as I have sighting dots on the camera top. I'm pleased that scratching is no longer a problem, thanks to glass in each tray.

Re: LF Pinhole - design and building

I find a masked bright light in front of the pinhole and a dim room makes it easier to work out if there is anything in the path to the film corners. My problems are either pinhole thickness or extreme angle effects, since I work with flat film. It sounds like you have more subtle issues.

Re: LF Pinhole - design and building

I always check with the sun, but they're always simple boxes or cans and easy to look inside with the top off. Thanks very much for starting this thread, I'm looking forward to reading it!

Compared to other beautiful cameras ( Like the amazing creations of Steve Irvine! ), mine are all made from mat board or foamcore or tin cans, although they have the advantage of being easily recyclable. My latest was from last WPPD.

Re: LF Pinhole - design and building

Seeing these examples with the curved film planes has me considering fabricating a camera in preparation for WWPD (my attempt last year went kablooey because I didn't notice that the sun was shining on my pinhole). I would most likely go for the simple materials like Ned's camera, and would probably make it to use 4X10 film (cut down 8X10 X-ray film). I am guessing the idea is to have the pinhole - to - film distance about equal from end to center to end, thereby keeping the exposure consistent the length of the film?

Since the film plane will be curved, what are the thoughts on curving the pinhole so that it matches the film curvature? Is that something that has been tried? I have never explored that idea so I don't know if there would be any benefit.